Anthropogenic threats include pollution, entanglement in fishing nets, and direct harvesting of their gill rakers for use in Chinese medicine.

They are protected in international waters by the Convention on Migratory Species of Wild Animals, but are more vulnerable closer to shore.

The name "manta" is Portuguese and Spanish for mantle (cloak or blanket), a type of blanket-shaped trap traditionally used to catch rays.

[10] They have horizontally flattened bodies with eyes on the sides of their heads behind the cephalic fins, and gill slits on their ventral surfaces.

[22] A pink manta ray has been observed in Australia's Great Barrier Reef and scientists believe this could be due to a genetic mutation causing erythrism.

The shoulder markings of M. alfredi are more rounded, while its ventral spots are located near the posterior end and between the gill slits, and the mouth is white or pale colored.

The spiracles typical of rays are vestigial and concealed by small flaps of skin, and mantas must keep swimming with their mouths open to keep oxygenated water passing over their gills.

Courtship is difficult to observe in this fast-swimming fish, although mating "trains" with multiple individuals swimming closely behind each other are sometimes seen in shallow water.

The mating sequence may be triggered by a full moon and seems to be initiated by a male following closely behind a female while she travels at around 10 km/h (6.2 mph).

After hatching, the pups remain in the oviduct and receive additional nutrition from milky secretions called histotroph.

The ray adopts a near-stationary position close to the coral surface for several minutes while the cleaner fish feed.

[39] Individual mantas may exhibit philopatry by revisiting the same cleaning station or feeding area repeatedly[40] and appear to have cognitive maps of their environment.

[11]: 36 Mantas are found in tropical and subtropical waters in all the world's major oceans, and also venture into temperate seas.

M. birostris lives mostly in the open ocean, travelling with the currents and migrating to areas where upwellings of nutrient-rich water increase prey concentrations.

[44] Fish that have been fitted with radio transmitters have traveled as far as 1,000 km (620 mi) from where they were caught, and descended to depths of at least 1,000 m (3,300 ft).

Because of their long lifespans and low reproductive rate, overfishing can severely reduce local populations with little likelihood that individuals from elsewhere will replace them.

[47] To fill the growing demand in Asia for gill rakers, targeted fisheries have developed in the Philippines, Indonesia, Mozambique, Madagascar, India, Pakistan, Sri Lanka, Brazil, and Tanzania.

[46] Each year, thousands of manta rays, primarily M. birostris, are caught and killed purely for their gill rakers.

A fisheries study in Sri Lanka and India estimated that over 1000 were being sold in the country's fish markets each year.

[48] By comparison, M. birostris populations at most of the key aggregation sites around the world are estimated to have significantly fewer than 1000 individuals.

[49] Targeted fisheries for manta rays in the Gulf of California, the west coast of Mexico, India, Sri Lanka, Indonesia, and the Philippines have reduced populations in these areas dramatically.

Because mantas must swim constantly to flush oxygen-rich water over their gills, they are vulnerable to entanglement and subsequent suffocation.

Other threats or factors that may affect manta numbers are climate change, tourism, pollution from oil spills, and the ingestion of microplastics.

[51][52] In 2011, mantas became strictly protected in international waters because of their inclusion in the Convention on Migratory Species of Wild Animals.

The CMS is an international treaty organization concerned with conserving migratory species and habitats on a global scale.

Although individual nations were already protecting manta rays, the fish often migrate through unregulated waters, putting them at increased risk from overfishing.

[64] One notable individual is "Nandi", a manta ray which was accidentally caught in shark nets off Durban, South Africa, in 2007.

[67] The Atlantis resort on Paradise Island, Bahamas, hosted a manta named "Zeus" that was used as a research subject for three years until it was released in 2008.

[70] Ray tourism benefits locals and visitors by raising awareness of natural resource management and educating them about the animals.

[72] Constant unregulated interactions with tourists can negatively affect them by disrupting ecological relationships and increasing disease transmission.